An image sensor device is a kind of semiconductor device that transforms optical images into electrical signals. Image sensor devices can be generally classified into charge coupled device (CCD) image sensor devices and complementary metal oxide semiconductor (CMOS) image sensor devices. Among these image sensor devices, the CMOS image sensor device comprises a photodiode for detecting incident light and transforming it into electrical signals, and logic circuits for transmitting and processing the electrical signals.
In a conventional image sensor device, a shallow trench isolation (STI) and a P-type doped region below the STI are adopted as electrical isolation between individual photodiodes. The individual photodiodes absorb various light wavelengths, resulting in the positions of photons converted into electrons in different depths. However, the photosensitive areas of the individual photodiodes are conventionally designed to have the same depth. Thus, the electrons located in a deeper position of the photosensitive areas can very easily overflow onto adjacent photosensitive areas and produce crosstalk problems, resulting in poor recovery of electronic signals. At the present time, the manner of increasing in the length of the shallow trench isolation (STI) or the P-type doped region below the STI in the substrate is used to solve the crosstalk problems. However, in an implantation process, when trying to deepen the length of the P-type doped region in the substrate, deviations can easily occur in the width, profile, or position of the P-type doped region deep in the substrate, and this can generate additional interference inhibiting signal recovery. As a result, this method is not effective in improving photosensitive efficiency.
Therefore, development of an image sensor device capable of effectively improving photosensitive efficiency is desirable.